This thesis describes a system that can be used for the decoding of a three dimensional audio recording over headphones or two, or more, speakers. A literature review of psychoacoustics and a review (both historical and current) of surround sound systems is carried out. The need for a system which is platform independent is discussed, and the proposal for a system based on an amalgamation of Ambisonics, binaural and transaural reproduction schemes is given. In order for this system to function optimally, each of the three systems rely on providing the listener with the relevant psychoacoustic cues. The conversion from a five speaker ITU array to binaural decode is well documented but pair-wise panning algorithms will not produce the correct lateralisation parameters at the ears of a centrally seated listener. Although Ambisonics has been well researched, no one has, as yet, produced a psychoacoustically optimised decoder for the standard irregular five speaker array as specified by the ITU as the original theory, as proposed by Gerzon and Barton (1992) was produced (known as a Vienna decoder), and example solutions given, before the standard had been decided on. In this work, the original work by Gerzon and Barton (1992) is analysed, and shown to be suboptimal, showing a high/low frequency decoder mismatch due to the method of solving the set of non-linear simultaneous equations. A method, based on the Tabu search algorithm, is applied to the Vienna decoder problem and is shown to provide superior results to those shown by Gerzon and Barton (1992) and is capable of producing multiple solutions to the Vienna decoder problem. During the write up of this report Craven (2003) has shown how 4th order circular harmonics (as used in Ambisonics) can be used to create a frequency independent panning law for the five speaker ITU array, and this report also shows how the Tabu search algorithm can be used to optimise these decoders further. A new method is then demonstrated using the Tabu search algorithm coupled with lateralisation parameters extracted from a binaural simulation of the Ambisonic system to be optimised (as these are the parameters that the Vienna system is approximating). This method can then be altered to take into account head rotations directly which have been shown as an important psychoacoustic parameter in the localisation of a sound source (Spikofski et al., 2001) and is also shown to be useful in differentiating between decoders optimised using the Tabu search form of the Vienna optimisations as no objective measure had been suggested. Optimisations for both Binaural and Transaural reproductions are then discussed so as to maximise the performance of generic HRTF data (i.e. not individualised) using inverse filtering methods, and a technique is shown that minimises the amount of frequency dependant regularisation needed when calculating cross-talk cancellation filters.

Ces travaux de thèse concernent la conception d’un dispositif de restitution sonore léger en salle usuelle, permettant la diffusion de signaux binauraux. La priorité du travail est la précision dans la reproduction du niveau et du timbre, avant la spatialisation du son. Afin d’assurer la compatibilité avec les signaux binauraux existants et pour proposer un système à faible nombre de canaux, la technologie transaurale est prise comme point de départ. Pour limiter la coloration introduite par la salle d’écoute, particulièrement gênante, il est proposé de placer les sources du système à proximité de l’auditeur afin de maximiser le rapport champ direct sur champ diffus. Ce placement inhabituel a plusieurs effets, parmi lesquels quatre ont été étudiés séparément : l’influence des filtres transauraux sur les sources électro-acoustiques, les variations inter-individuelles de morphologies, l’effet de salle et le placement de l’auditeur. Des tests d’écoute ont été réalisés pour une sélection de configurations, et les résultats ont permis d’implémenter des indicateurs objectifs représentatifs des réponses des auditeurs. La synthèse de ces indicateurs a permis de proposer trois configurations considérées comme optimales, et dont la combinaison pourrait être envisagée. / This work deals with the design of a 3D sound system involving a few number of loudspeaker and able to work inside any usual room, for reproducing binaural sounds. This system focuses on an accurate reproduction of perceived level and timbre, even before the sound spatialization. To ensure compatibility with binaural recordings and to achieve a system with a low number of loudspeakers, this work started from a transaural system. To avoid tone coloration induced by the listening room, the sound sources are placed close to the listener, thus maximizing the energy ratio between direct and diffuse fields. This has consequences on other aspects, four of which are considered separately: inter-individual morphological variations, demands on the electro-acoustic sources, room effect and misalignment of the listener. Some configurations have been evaluated in listening tests, and objective indicators are deduced from these results. The generalization allows to propose three configurations considered as optimal, and which might be combined.

This thesis concerns itself with a phenomenon found in film music that can be described as audible diegetic transitions. In short, an audible diegetic transition occurs when film music shifts from one implied musical placement to another by changing its pre­sented sound quality. This occurs predominantly through the employment of music that is pre-existing in relation to the release of the film where the music is utilised. These audible diegetic transitions are categorised as aural displacements and transaural dis­placements which are both anchored in previous re­search concerning stable musical place­ments. In order to answer the research questions regarding technical aspects and narra­tological implications, the thesis is centred around a film music analysis. The de­marcation of said analysis uses pre-existing songs from the film Joker (Philips, 2019) as its main focus. In order to provide a colourful and meaningful discussion the selected material also contains a variety of examples from other films. The analysis shows that the selected audible diegetic transitions can provide narra­tological implications both for a film as a whole and for a specific scene or se­quence in any film. In Joker specifically, the audible diegetic transitions arguably contain the narra­to­logi­cal im­plication of adding to the retrospective and unreliable narration, which is im­port­ant for the story of the film. The thesis also argues that the technical aspects of the ana­lysed audible diegetic transitions can be condensed into being either diegetic to comm­en­tary, or vice versa. Diegetic music is, in this context, defined as music that is im­­­­plied as being heard in the acoustic space of the story-world, whereas commen­tary music is an um­brella term defined as music that is not implied being heard in the acous­tic space of the story-world. The analysis shows that these transitions can transpire either instantly or gra­­­dually with the change of sound quality from being either narrow or wide. These tech­nical aspects contribute in under­standing the narratological im­plications of said au­dible diegetic transition by categorising them as either emotive or groun­ding. Both of these narratological implications can be concluded and described as swift enforcers of the relationship be­tween the one consuming the film and the char­acters, or lo­cations, of the film they are con­­­­suming. Audible diegetic transitions figura­tively breach the fourth wall that is the screen.